linux-kernel - Re: [PATCH 3/4] SUNRPC: Replace dprintk() call site in xs_data

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Message-ID: <Yt67gCcZfOEJizay@kernel.org>
Date:   Mon, 25 Jul 2022 12:49:20 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Chuck Lever III <chuck.lever@...cle.com>,
        Trond Myklebust <trondmy@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 3/4] SUNRPC: Replace dprintk() call site in xs_data_ready

Em Fri, Jul 22, 2022 at 04:22:12PM -0400, Steven Rostedt escreveu:
> [ Added the user space perf folks ]
> 
> On Fri, 22 Jul 2022 18:45:30 +0000
> Chuck Lever III <chuck.lever@...cle.com> wrote:
> 
> > >> +TRACE_EVENT(xs_data_ready,
> > >> +  TP_PROTO(
> > >> +  const struct rpc_xprt *xprt
> > >> +  ),
> > >> +
> > >> +  TP_ARGS(xprt),
> > >> +
> > >> +  TP_STRUCT__entry(
> > >> +  __sockaddr(addr, xprt->addrlen)
> > >> +  ),
> > >> +
> > >> +  TP_fast_assign(
> > >> +  __assign_sockaddr(addr, &xprt->addr, xprt->addrlen);
> > >> +  ),
> > >> +
> > >> +  TP_printk("peer=%pISpc", __get_sockaddr(addr))  
> > > 
> > > NACK. Please resolve and store the string up front instead of storing
> > > the sockaddr. Most versions of perf can't resolve those kernel-specific
> > > %p printks and just end up barfing on them.  
> > 
> > Interesting. We added get_sockaddr() to avoid this issue in
> > trace-cmd. Sounds like perf needs to be fixed up too, or
> > maybe this is another case of having an old libtraceevent?
> > 
> > Meanwhile, I can revert this back to the old way of handling
> > presentation addresses.
> > 
> 
> Hmm, I thought that perf now uses the external libtraceevent.
> 
> Perhaps it hasn't been updated to the latest release that has the ability
> to parse this.
> 
> Maybe just install
> 
>   git://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git

To use it one has to use:

  make -C tools/perf LIBTRACEEVENT_DYNAMIC=1

Then we get it linked with libtraceevent-devel:

$ ldd ~/bin/perf | grep traceevent
	libtraceevent.so.1 => /lib64/libtraceevent.so.1 (0x00007faa50f93000)
$

Perhaps it'd be better to check if libtracevent-devel is installed and
use it, falling back to tools/lib/traceevent/ and then adding a warning
that the in-tree codebase is being used?

- Arnaldo